Most identification cards now being made are printed by dye diffusion, thermal transfer (D2T2) printers on vinyl or polyester cards. One problem with these cards has been the relatively simple ability to tamper with the printing on the card. It is a fairly simple procedure to remove the printed images and overlays by abrasion of the surface of the card. The card can then be reprinted with a new polymer layer using a D2T2 printer. It is exceedingly difficult to detect these alterations.
Color has been used as a security feature to prevent counterfeiting or tampering with various media. For example, U.S. Pat. No. 5,346,258 teaches use of colored "confusion patterns" above and below play indicia on a lottery ticket. Tampering with the ticket damages the confusion pattern.
In U.S. Pat. No. 5,403,039 Borowski, Jr. et al. teach a thermochromic layer over printing on a lottery ticket or the like. A user can observe the presence or absence of a reversible color change in the thermochromic layer. Tampering with the card affects the thermochromic layer which would be visible when a color reversal is attempted.
Presently, no technology adequately addresses the problems with tampering of identification cards.
A primary object of the invention is to develop an identification card that will be highly resistant to tampering. It is a further object of the invention that the detection of any tampering done to the card be detectable in a manner that is both simple and rapid. It is a final object of the invention to be able to effect this detection even if the printing on the surface of the card has been removed and a new layer of printed material added onto the surface of the card.